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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Have FTS assign extremely high costs to plans that feature unusable MATCH constraints. This discourages the planner from choosing such plans, which lead to "unable to use function MATCH in the requested context" errors.
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SHA1: fa8be488a3ad290722dae7a1a7396c77277b2149
User & Date: dan 2014-01-04 14:46:39
Context
2014-01-04
15:17
Improvements to the column-cache for nested AND/OR operators. check-in: 4e725f53 user: drh tags: trunk
14:46
Have FTS assign extremely high costs to plans that feature unusable MATCH constraints. This discourages the planner from choosing such plans, which lead to "unable to use function MATCH in the requested context" errors. check-in: fa8be488 user: dan tags: trunk
14:42
Instead of having the planner ignore plans with unusable MATCH constraints, have FTS assign extremely high costs to such plans in order to discourage the planner from using them. Closed-Leaf check-in: 24f84b38 user: dan tags: avoid-unusable-match
2014-01-03
16:03
Avoid some unnecessary OP_SCopy operations when inserting into a table with multiple indices. check-in: 429018b1 user: drh tags: trunk
Changes
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Changes to ext/fts3/fts3.c.

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  int argc,                       /* Number of elements in argv array */
  const char * const *argv,       /* xCreate/xConnect argument array */
  sqlite3_vtab **ppVtab,          /* OUT: New sqlite3_vtab object */
  char **pzErr                    /* OUT: sqlite3_malloc'd error message */
){
  return fts3InitVtab(1, db, pAux, argc, argv, ppVtab, pzErr);
}














/* 
** Implementation of the xBestIndex method for FTS3 tables. There
** are three possible strategies, in order of preference:
**
**   1. Direct lookup by rowid or docid. 
**   2. Full-text search using a MATCH operator on a non-docid column.
................................................................................
  ** strategy is possible.
  */
  pInfo->idxNum = FTS3_FULLSCAN_SEARCH;
  pInfo->estimatedCost = 5000000;
  for(i=0; i<pInfo->nConstraint; i++){
    int bDocid;                 /* True if this constraint is on docid */
    struct sqlite3_index_constraint *pCons = &pInfo->aConstraint[i];
    if( pCons->usable==0 ) continue;














    bDocid = (pCons->iColumn<0 || pCons->iColumn==p->nColumn+1);

    /* A direct lookup on the rowid or docid column. Assign a cost of 1.0. */
    if( iCons<0 && pCons->op==SQLITE_INDEX_CONSTRAINT_EQ && bDocid ){
      pInfo->idxNum = FTS3_DOCID_SEARCH;
      pInfo->estimatedCost = 1.0;







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  int argc,                       /* Number of elements in argv array */
  const char * const *argv,       /* xCreate/xConnect argument array */
  sqlite3_vtab **ppVtab,          /* OUT: New sqlite3_vtab object */
  char **pzErr                    /* OUT: sqlite3_malloc'd error message */
){
  return fts3InitVtab(1, db, pAux, argc, argv, ppVtab, pzErr);
}

/*
** Set the pIdxInfo->estimatedRows variable to nRow. Unless this
** extension is currently being used by a version of SQLite too old to
** support estimatedRows. In that case this function is a no-op.
*/
static void setEstimatedRows(sqlite3_index_info *pIdxInfo, i64 nRow){
#if SQLITE_VERSION_NUMBER>=3008002
  if( sqlite3_libversion_number()>=3008002 ){
    pIdxInfo->estimatedRows = nRow;
  }
#endif
}

/* 
** Implementation of the xBestIndex method for FTS3 tables. There
** are three possible strategies, in order of preference:
**
**   1. Direct lookup by rowid or docid. 
**   2. Full-text search using a MATCH operator on a non-docid column.
................................................................................
  ** strategy is possible.
  */
  pInfo->idxNum = FTS3_FULLSCAN_SEARCH;
  pInfo->estimatedCost = 5000000;
  for(i=0; i<pInfo->nConstraint; i++){
    int bDocid;                 /* True if this constraint is on docid */
    struct sqlite3_index_constraint *pCons = &pInfo->aConstraint[i];
    if( pCons->usable==0 ){
      if( pCons->op==SQLITE_INDEX_CONSTRAINT_MATCH ){
        /* There exists an unusable MATCH constraint. This means that if
        ** the planner does elect to use the results of this call as part
        ** of the overall query plan the user will see an "unable to use
        ** function MATCH in the requested context" error. To discourage
        ** this, return a very high cost here.  */
        pInfo->idxNum = FTS3_FULLSCAN_SEARCH;
        pInfo->estimatedCost = 1e50;
        setEstimatedRows(pInfo, ((sqlite3_int64)1) << 50);
        return SQLITE_OK;
      }
      continue;
    }

    bDocid = (pCons->iColumn<0 || pCons->iColumn==p->nColumn+1);

    /* A direct lookup on the rowid or docid column. Assign a cost of 1.0. */
    if( iCons<0 && pCons->op==SQLITE_INDEX_CONSTRAINT_EQ && bDocid ){
      pInfo->idxNum = FTS3_DOCID_SEARCH;
      pInfo->estimatedCost = 1.0;

Added test/fts3join.test.





































































































































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# 2014 January 4
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#*************************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is testing the FTS3 module.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set ::testprefix fts3join

# If SQLITE_ENABLE_FTS3 is defined, omit this file.
ifcapable !fts3 {
  finish_test
  return
}

do_execsql_test 1.0 {
  CREATE VIRTUAL TABLE ft1 USING fts4(x);
  INSERT INTO ft1 VALUES('aaa aaa');
  INSERT INTO ft1 VALUES('aaa bbb');
  INSERT INTO ft1 VALUES('bbb aaa');
  INSERT INTO ft1 VALUES('bbb bbb');

  CREATE TABLE t1(id, y);
  INSERT INTO t1 VALUES(1, 'aaa');
  INSERT INTO t1 VALUES(2, 'bbb');
}

do_execsql_test 1.1 {
  SELECT docid FROM ft1, t1 WHERE ft1 MATCH y AND id=1;
} {1 2 3}

do_execsql_test 1.2 {
  SELECT docid FROM ft1, t1 WHERE ft1 MATCH y AND id=1 ORDER BY docid;
} {1 2 3}

do_execsql_test 2.0 {
  CREATE VIRTUAL TABLE ft2 USING fts4(x);
  CREATE VIRTUAL TABLE ft3 USING fts4(y);

  INSERT INTO ft2 VALUES('abc');
  INSERT INTO ft2 VALUES('def');
  INSERT INTO ft3 VALUES('ghi');
  INSERT INTO ft3 VALUES('abc');
}

do_execsql_test 2.1 { SELECT * FROM ft2, ft3 WHERE x MATCH y; } {abc abc}
do_execsql_test 2.2 { SELECT * FROM ft2, ft3 WHERE y MATCH x; } {abc abc}
do_execsql_test 2.3 { SELECT * FROM ft3, ft2 WHERE x MATCH y; } {abc abc}
do_execsql_test 2.4 { SELECT * FROM ft3, ft2 WHERE y MATCH x; } {abc abc}

do_catchsql_test 2.5 { 
  SELECT * FROM ft3, ft2 WHERE y MATCH x AND x MATCH y; 
} {1 {unable to use function MATCH in the requested context}}

finish_test